1. Field of the Invention
The present invention relates to a manufacturing method of a liquid crystal display device (LCD), in particular, an active matrix liquid crystal display device (hereinafter abbreviated as AM-LCD) that uses a semiconductor thin film. The invention can be applied to an electro-optical device having such a display device.
2. Description of the Related Art
In this specification, the term xe2x80x9csemiconductor devicexe2x80x9d means every device that functions by using a semiconductor. Therefore, each of the above-mentioned display device and electro-optical device is included in the scope of the semiconductor device. However, in this specification, the terms xe2x80x9cdisplay devicexe2x80x9d and xe2x80x9celectro-optical devicexe2x80x9d are used for the sake of discrimination.
In recent years, projectors or the like that use an AM-LCD as a projection-type display have been developed extensively. Further, the demand for AM-LCDs as direct-view displays for mobile computers and video cameras is now increasing.
FIGS. 2A and 2B schematically show the configuration of a pixel matrix circuit in a conventional AM-LCD. The pixel matrix circuit, which constitutes an image display area of the AM-LCD, is a circuit in which thin-film transistors (TFTs) for controlling electric fields applied to a liquid crystal are arranged in matrix form.
FIG. 2A is a top view of the pixel matrix circuit. The regions that are enclosed by a plurality of gate lines 201 extending in the horizontal direction and a plurality of source lines 202 extending in the vertical direction are pixel regions. TFTs 203 are formed at the respective intersections of the gate lines 201 and the source lines 202. Pixel electrodes 204 are connected to the respective TFTs.
Thus, the pixel matrix circuit consists of a plurality of pixel regions that are enclosed by the gate lines 201 and the source lines 202 and are thereby arranged in matrix form, and each pixel region is provided with a TFT 203 and a pixel electrode 204.
FIG. 2B shows a sectional structure of the pixel matrix circuit. In FIG. 2B, reference numeral 205 denotes a substrate having an insulating surface and numerals 206 and 207 denote pixel TFTs formed on the substrate 205. The pixel TFTs 206 and 207 correspond to the TFTs 203 in FIG. 2A.
Pixel electrodes 208 and 209, which correspond to the pixel electrodes 204 in FIG. 2A, are connected to the respective pixel TFTs 206 and 207. Usually, the pixel electrodes 208 and 209 are obtained by patterning a single metal thin film.
Therefore, the pixel matrix circuit having the conventional structure necessarily includes electrode boundary portions (hereinafter referred to simply as boundary portions) 210 and 211 between the pixel electrodes 208, 209, etc.; there necessarily occur steps corresponding to the film thickness of the pixel electrodes 208 and 209. The steps of this type may cause alignment failures of a liquid crystal material, leading to a disordered display image. Further, diffused reflection at the step portions of incident light may deteriorate the contrast or reduce the efficiency of light utilization.
As seen from FIG. 2B, above the semiconductor elements and the intersections of the wiring lines, the pixel electrodes 208 and 209 are formed so as to reflect their shapes. The steps of this type may also cause the above-mentioned problems.
In particular, the above problems appear more remarkably in projection-type displays for projectors and the like, because an image of a small (about 1 to 2 inches), very-high-resolution display is projected in an enlarged manner.
Conventionally, to deal with the above problems, the contrast ratio is increased by shielding regions where an image may be disordered with a black mask (or a black matrix). In recent years, because the device miniaturization has advanced and hence a high degree of controllability of shield regions is required to provide a large aperture ratio, a configuration in which a black mash is formed on a TFT-side substrate is the mainstream.
However, forming a black mash on a TFT-side substrate causes various problems such as an increased number of patterning steps, an increase in parasitic capacitance, and a decrease in aperture ratio. Therefore, a technique for securing a high contract ratio without causing above-mentioned problems is now desired.
The present invention has been made in view of above circumstance and therefore, an object of the present invention is to solve the above problems in the art and to thereby enable, with a simple means, formation of a very-high-resolution AM-LCD.
According to a first aspect of the invention, there is provided a manufacturing method of a semiconductor device, comprising the steps of planarizing an insulating film formed on a substrate having an insulating surface; forming a plurality of electrodes on the insulating film; forming an insulating layer so as to cover the plurality of electrodes; and planarizing surfaces of the plurality of electrodes and a surface of the insulating layer so that they become flush with each other, thereby filling boundary portions between the plurality of electrodes with the insulating layer.
There is also provided a manufacturing method of a semiconductor device having a first substrate, a second, transparent substrate, and a liquid crystal layer held between the first and second substrates, comprising the steps of planarizing an insulating film formed on the first substrate; forming striped electrodes on the insulating film; forming an insulating layer so as to cover the striped electrodes; and planarizing surfaces of the striped electrodes and a surface of the insulating layer so that they become flush with each other, thereby filling boundary portions between the striped electrodes with the insulating layer.
There is also provided a manufacturing method of a semiconductor device, comprising the steps of forming a plurality of semiconductor elements on a substrate having an insulating surface; forming an interlayer insulating film; planarizing the interlayer insulating film; forming pixel electrodes that are electrically connected to the respective semiconductor elements on the interlayer insulating film; forming an insulating layer so as to cover the pixel electrodes; and planarizing surfaces of the pixel electrodes and a surface of the insulating layer so that they become flush with each other, thereby filling boundary portions between the pixel electrodes with the insulating layer.
There is further provided a manufacturing method of a semiconductor device having a substrate that has a plurality of semiconductor elements arranged in matrix form and a plurality of pixel electrodes connected to the respective semiconductor elements, and a liquid crystal layer held on the substrate, comprising the steps of forming an interlayer insulating film; planarizing the interlayer insulating film; forming pixel electrodes that are electrically connected to the respective semiconductor elements on the interlayer insulating film; forming an insulating layer so as to cover the pixel electrodes; and planarizing surfaces of the pixel electrodes and a surface of the insulating layer so that they become flush with each other, thereby filling boundary portions between the pixel electrodes with the insulating layer.
According to a second aspect of the invention, there is provided a semiconductor device comprising a plurality of electrodes formed on a substrate having an insulating surface; a DLC film covering the plurality of electrodes; and an insulating layer buried in boundary portions of the plurality of electrodes.
There is also provided a semiconductor device comprising a first substrate; a second, transparent substrate; a liquid crystal layer held between the first and second substrates; striped electrodes formed on each of the first and second substrates; a DLC film covering the striped electrodes; and an insulating layer buried in boundary portions of the striped electrodes.
There is also provided a semiconductor device comprising a plurality of semiconductor elements formed in matrix form on a substrate having an insulating surface; a plurality of pixel electrodes connected to the respective semiconductor elements; a DLC film covering the pixel electrodes; and an insulating layer buried in boundary portions of the pixel electrodes.
There is further provided a semiconductor device comprising a substrate having a plurality of semiconductor elements arranged in matrix form and a plurality of pixel electrodes connected to the respective semiconductor elements; a liquid crystal layer held on the substrate; a DLC film covering the pixel electrodes; and an insulating layer buried in boundary portions of the pixel electrodes.
Still according to the second aspect of the invention, there is provided a manufacturing method of a semiconductor device, comprising the steps of forming a plurality of electrodes on a substrate having an insulating surface; forming a DLC film to cover a plurality of electrodes; forming an insulating layer on the DLC film; and planarizing the insulating layer so that a surface of the DLC film and a surface of the insulating layer become flush with each other, thereby filling boundary portions of the plurality of electrodes with the insulating layer.
There is also provided a manufacturing method of a semiconductor device having a first substrate, a second, transparent substrate, and a liquid crystal layer held between the first and second substrates, comprising the steps of forming striped electrodes on the first substrate; forming a DLC film to cover the striped electrodes; forming an insulating layer on the DLC film; and planarizing the insulating layer so that a surface of the DLC film and a surface of the insulating layer become flush with each other, thereby filling boundary portions of the striped electrodes with the insulating layer.
There is also provided a manufacturing method of a semiconductor device, comprising the steps of forming a plurality of semiconductor elements on a substrate having an insulating surface; forming a plurality of pixel electrodes that are electrically connected to the respective semiconductor elements; forming a DLC film to cover the pixel electrodes; forming an insulating layer on the DLC film; and planarizing the insulating layer so that a surface of the DLC film and a surface of the insulating layer become flush with each other, thereby filling boundary portions of the pixel electrodes with the insulating layer.
There is further provided a manufacturing method of a semiconductor device having a substrate that has a plurality of semiconductor elements arranged in matrix form and a plurality of pixel electrodes connected to the respective semiconductor elements, and a liquid crystal layer held on the substrate, comprising the steps of forming a DLC film to cover the pixel electrodes; forming an insulating layer on the DLC film; and planarizing the insulating layer so that a surface of the DLC film and a surface of the insulating layer become flush with each other, thereby filling boundary portions of the plurality of the pixel electrodes with the insulating layer.
In the above description of the invention, the term DLC is an abbreviation of xe2x80x9cdiamond-like carbon.xe2x80x9d A DLC film is therefore a thin film that is made only or mainly of carbon and that exhibits diamond-like physical properties such as high hardness. This material is also called i-carbon and mainly has sp3 bonds.
The hardness (Vickers hardness) of a DLC film is as high as 2,000 kg/mm2 or more and its friction coefficient is 0.4 or less. Therefore, DLC films are used as protection films and lubrication films. However, if the hydrogen content is excessively large, a DLC film becomes too soft to be used in the invention.
A DLC film exhibits a characteristic feature in Raman data. FIG. 18 shows Raman data of a DLC film used in the invention, in which the vertical axis represents relative intensity. A measurement was conducted in the air at the room temperature by using an Ar+ laser (laser beam diameter: 1 xcexcm; output power: 1.0 mW; slit width: 100 xcexcm). The accumulation time was 300 secxc3x972.
As seen from FIG. 18, a DLC film has a broad Raman spectrum extending on both sides of a peak at about 1,550 cmxe2x88x921. The fact that the Raman spectrum is asymmetrical with respect to the peak 1,550 cmxe2x88x921 is also a feature of a DLC film.
Raman data of diamond has a sharp peak at about 1,330 cmxe2x88x921 and hence is easily distinguished from that of a DLC film. Further, a carbon film that is rendered soft due to loss of a crystal structure (regarded as a different material than a DLC film) has two Raman peaks or no clear Raman peak and hence can easily be distinguished from a DLC film.
In connection with the above description of the invention, a typical example of the liquid crystal layer holding state is such that a liquid crystal layer is held between a substrate (first substrate) having a plurality of pixel electrodes and an opposed substrate (second substrate) that confronts the first substrate. Where a PDLC (polymer dispersion liquid crystal) is used as a liquid crystal layer, there may occur a case that the second substrate is not necessary, because the liquid crystal layer itself is rendered in a solid state.
The typical example of the semiconductor element is a thin-film transistor (TFT). In addition, the semiconductor element may be an insulated-gate field-effect transistor (IGFET), a thin-film diode, an MIM (metal-insulator-metal) element, a varistor element, or the like.